Results 1  10
of
13
Deletion along Trajectories
 Theor. Comp. Sci
, 2003
"... We describe a new way to model deletions on formal languages, called deletion along trajectories. We examine its closure properties, and show that it serves as an inverse to shuffle on trajectories, recently introduced by Mateescu et al. This leads to results on the decidability of equations of the ..."
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Cited by 14 (5 self)
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We describe a new way to model deletions on formal languages, called deletion along trajectories. We examine its closure properties, and show that it serves as an inverse to shuffle on trajectories, recently introduced by Mateescu et al. This leads to results on the decidability of equations of the form L T X = R, where L; R are regular languages and X is unknown. 1
The Descriptive Complexity Approach to LOGCFL
, 1998
"... Building upon the known generalizedquantifierbased firstorder characterization of LOGCFL, we lay the groundwork for a deeper investigation. Specifically, we examine subclasses of LOGCFL arising from varying the arity and nesting of groupoidal quantifiers. Our work extends the elaborate theory ..."
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Cited by 11 (5 self)
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Building upon the known generalizedquantifierbased firstorder characterization of LOGCFL, we lay the groundwork for a deeper investigation. Specifically, we examine subclasses of LOGCFL arising from varying the arity and nesting of groupoidal quantifiers. Our work extends the elaborate theory relating monoidal quantifiers to NC and its subclasses. In the absence of the BIT predicate, we resolve the main issues: we show in particular that no single outermost unary groupoidal quantifier with FO can capture all the contextfree languages, and we obtain the surprising result that a variant of Greibach's "hardest contextfree language" is LOGCFLcomplete under quantifierfree BITfree projections. We then prove that FO with unary groupoidal quantifiers is strictly more expressive with the BIT predicate than without. Considering a particular groupoidal quantifier, we prove that firstorder logic with majority of pairs is strictly more expressive than firstorder with major...
Recognizing boolean closed Atree languages with membership conditional mechanism
 In 14 th International Conference on Rewriting Techniques and Applications, volume 2706 of Lecture notes in computer science
, 2003
"... Abstract. This paper provides an algorithm to compute the complement of tree languages recognizable with ATA (tree automata with associativity axioms [16]). Due to this closure property together with the previously obtained results, we know that the class is boolean closed, while keeping recognizab ..."
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Cited by 10 (1 self)
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Abstract. This paper provides an algorithm to compute the complement of tree languages recognizable with ATA (tree automata with associativity axioms [16]). Due to this closure property together with the previously obtained results, we know that the class is boolean closed, while keeping recognizability of Aclosures of regular tree languages. In the proof of the main result, a new framework of tree automata, called sequencetree automata, is introduced as a generalization of Lugiez and Dal Zilio’s multitree automata [14] of an associativity case. It is also shown that recognizable Atree languages are closed under a onestep rewrite relation in case of ground Aterm rewriting. This result allows us to compute an underapproximation of Arewrite descendants of recognizable Atree languages with arbitrary accuracy. 1
Synchronized Product of Linear Bounded Machines
 In FCT, volume 1684 of LNCS
, 1999
"... This paper introduces a class of graphs defined as the models of a peculiar kind of linear bounded machines that read their input performing all computations on work tapes. ..."
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Cited by 8 (1 self)
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This paper introduces a class of graphs defined as the models of a peculiar kind of linear bounded machines that read their input performing all computations on work tapes.
Commutation Problems on Sets of Words and Formal Power Series
, 2002
"... We study in this thesis several problems related to commutation on sets of words and on formal power series. We investigate the notion of semilinearity for formal power series in commuting variables, introducing two families of series  the semilinear and the bounded series  both natural generaliza ..."
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Cited by 4 (3 self)
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We study in this thesis several problems related to commutation on sets of words and on formal power series. We investigate the notion of semilinearity for formal power series in commuting variables, introducing two families of series  the semilinear and the bounded series  both natural generalizations of the semilinear languages, and we study their behaviour under rational operations, morphisms, Hadamard product, and difference. Turning to commutation on sets of words, we then study the notions of centralizer of a language  the largest set commuting with a language , of root and of primitive root of a set of words. We answer a question raised by Conway more than thirty years ago  asking whether or not the centralizer of any rational language is rational  in the case of periodic, binary, and ternary sets of words, as well as for rational ccodes, the most general results on this problem. We also prove that any code has a unique primitive root and that two codes commute if and only if they have the same primitive root, thus solving two conjectures of Ratoandromanana, 1989. Moreover, we prove that the commutation with an ccode X can be characterized similarly as in free monoids: a language commutes with X if and only if it is a union of powers of the primitive root of X.
ErrorDetecting Properties of Languages
 Theoretical Computer Science
, 2002
"... The language property of errordetection ensures that the communications medium cannot transform a word of the language to another word of the language. In this paper we provide some insights on the notion of errordetection from a language theoretic point of view. We de ne certain errordetecting p ..."
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Cited by 3 (2 self)
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The language property of errordetection ensures that the communications medium cannot transform a word of the language to another word of the language. In this paper we provide some insights on the notion of errordetection from a language theoretic point of view. We de ne certain errordetecting properties of languages and codes including the notion of errordetection with nite delay which is a natural extension of unique decodability with nite delay. We obtain results about the errordetecting capabilities of regular and other languages, and of known classes of codes. Moreover, we consider the problem of estimating the optimal redundancy of in nite languages with the property of detecting errors of the deletion type.
Varieties of crossing dependencies: Structure dependence and mild context sensitivity
 Cognitive Science
, 2004
"... Four different kinds of grammars that can define crossing dependencies in human language are compared here: (i) context sensitive rewrite grammars with rules that depend on context; (ii) matching grammars with constraints that filter the generative structure of the language, (iii) copying grammars w ..."
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Cited by 3 (2 self)
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Four different kinds of grammars that can define crossing dependencies in human language are compared here: (i) context sensitive rewrite grammars with rules that depend on context; (ii) matching grammars with constraints that filter the generative structure of the language, (iii) copying grammars which can copy structures of unbounded size, and (iv) generating grammars in which crossing dependencies are generated from a finite lexical basis. Context sensitive rewrite grammars are syntactically, semantically and computationally unattractive. Generating grammars have a collection of nice properties that ensure they define only “mildly context sensitive” languages, and Joshi has proposed that human languages have those properties too. But for certain distinctive kinds of crossing dependencies in human languages, copying or matching analyses predominate. Some results relevant to the viability of mildly context sensitive analyses and some open questions are reviewed.
Grammar Systems as Language Analyzers and Recursively Enumerable Languages
, 1999
"... We consider parallel communicating grammar systems which consist of several grammars and perform derivation steps, where each of the grammars works in a parallel and synchronized manner on its own sentential form, and communication steps, where a transfer of sentential forms is done. We discuss ..."
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Cited by 2 (0 self)
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We consider parallel communicating grammar systems which consist of several grammars and perform derivation steps, where each of the grammars works in a parallel and synchronized manner on its own sentential form, and communication steps, where a transfer of sentential forms is done. We discuss accepting and analyzing versions of such grammar systems with contextfree productions and present characterizations of the family of recursively enumerable languages by them.
Celllike Versus Tissuelike P Systems by Means of Sevilla Carpets
"... Summary. Sevilla Carpets are a handy tool for comparing computations performed by different systems solving the same problem. Such Sevilla Carpets provide on one hand quantitative information through parameters such as Weight, Surface and Average weight, and on the other hand they also provide a fas ..."
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Cited by 2 (2 self)
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Summary. Sevilla Carpets are a handy tool for comparing computations performed by different systems solving the same problem. Such Sevilla Carpets provide on one hand quantitative information through parameters such as Weight, Surface and Average weight, and on the other hand they also provide a fast glimpse on the complexity of the computation thanks to their graphical representation. Up to now, Sevilla Carpets were only used on Celllike P systems. In this paper we present a first comparison by means of Sevilla Carpets of the computations of three P systems (designed within different models), all of them solving the same instance of the Subset Sum problem. Two of these solutions use Celllike P systems with active membranes, while the third one uses Tissuelike P systems with cell division. 1
The Descriptive Complexity Approach to LOGCFL
, 1999
"... Building upon the known generalizedquantifierbased firstorder characterization of LOGCFL, we lay the groundwork for a deeper investigation. Specifically, we examine subclasses of LOGCFL arising from varying the arity and nesting of groupoidal quantifiers. Our work extends the elaborate theory ..."
Abstract

Cited by 1 (0 self)
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Building upon the known generalizedquantifierbased firstorder characterization of LOGCFL, we lay the groundwork for a deeper investigation. Specifically, we examine subclasses of LOGCFL arising from varying the arity and nesting of groupoidal quantifiers. Our work extends the elaborate theory relating monoidal quantifiers to NC 1 and its subclasses. In the absence of the BIT predicate, we resolve the main issues: we show in particular that no single outermost unary groupoidal quantifier with FO can capture all the contextfree languages, and we obtain the surprising result that a variant of Greibach's "hardest contextfree language" is LOGCFLcomplete under quantifierfree BITfree projections. We then prove that FO with unary groupoidal quantifiers is strictly more expressive with the BIT predicate than without. Considering a particular groupoidal quantifier, we prove that firstorder logic with majority of pairs is strictly more expressive than firstorder with major...